Shot tube for die-cast machine

ABSTRACT

A shot tube includes an inner bore for delivering molten material into a die-cast mold. The shot tube has an outer peripheral surface with at least one surface for receiving a locking member to lock the shot tube into an aperture in a fixed mold portion and an alignment structure for properly aligning the shot tube in the fixed mold portion. An opening receives molten material into the inner bore.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/767,011, filed Aug. 11, 2015, which claims priority to U.S.Provisional Application 61/775,725, filed Mar. 6, 2014.

BACKGROUND

This application relates to a shot tube for injecting molten metal intoa die-cast mold.

Die casting is a metal casting technique that employs the use ofpermanent, reusable molds in which molten alloys are injected andcompressed into the cavities to form the desired component. The die castsystem is comprised of multiple components: the molds, the shot tube,the shot rod and piston, the frame of the machine, a hydraulic system,pneumatic system, and a programmable logic controller to control theinterconnected systems

Die-cast molds are known and utilized to form any number of components.A die-cast machine is comprised of a fixed platen and a moving platen.In a split die set one half of the mold mounts the stationary platen andthe second half to the moveable platen. The moving platen is actuated byhydraulic piston, and mechanical clamping system to position themoveable die half in the appropriate position during each phase of thedie casting process. A singular or array of cavities are formed betweenthe two die halves in the shape of a component which is to be cast.

The desired alloy is liquefied by a variety of methods and istransferred to or directly poured through the opening in a shot tube.The molten alloy is added to the desired fill level for the component,the hydraulic injection system is activated, and the piston pushes themolten metal along the shot tube delivering the molten material into thecavity. As the molten metal begins to solidify, an intensification cyclecan be used to further compress the semisolid alloy into the die cavityto minimize casting defects such as shrinkage and non-fill of thecavities. Upon solidification the component is formed into the shape ofthe cavity.

Historically, the shot tubes have been mounted to the fixed platen intraditional machines that operate in air. While this is suitable for lowtemperature alloy system, the stack up of tolerances that causesmisalignment and gaps is extremely problematic for quick solidifyinghigh temperature alloys. The desire to improve the quality of existingalloys and the opportunity to cast higher temperature capable alloyssuch as: steels, iron-nickel super alloys, nickel super alloys, andcobalt super alloys creates the need to operate the die casting systemin a vacuum to ensure metallurgical quality and elimination of defectssuch as dross and ceramic inclusions from these alloy systems.

Conventional mounting of the shot tube poses significant challenges as aresult of need to operate the system in a vacuum. Mounting the tube inthe traditional manner would require extensive sealing between the tubeand the platen to prevent the flow of an oxidizing atmosphere into thetube. In order to minimize vacuum leaks and maintenance of the tube analternative method of mounting and aligning the tube is required toensure optimal operation and serviceability of the equipment.

In one particular die-cast system, an electron beam device is utilizedto melt an ingot of metal within a vacuum chamber. The molten metaldrips into a water cooled copper crucible as the ingot is superheated bythe electron beam. When a sufficient amount of material has filled thecrucible, the electron beam sweeps across the surface until the systemhas achieved the desired temperature, the dross is swept to the rear ofthe crucible, the system is tilted and the molten metal is pouredthrough the opening in the shot tube. In this embodiment, the fixedplatan does not easily mount the shot tube.

SUMMARY

In a featured embodiment, a shot tube has an inner bore for deliveringmolten material into a die-cast mold, an outer peripheral surface withat least one surface for receiving a locking member to lock the shottube into a fixed mold portion and an alignment structure for properlyaligning the shot tube in the fixed mold portion. The shot tube furtherhas an opening for receiving molten material into the inner bore.

In another embodiment according to the previous embodiment, the surfaceincludes a pair of surfaces formed at an outer periphery of the shottube.

In another embodiment according to any of the previous embodiments, thepair of surfaces are flats.

In another embodiment according to any of the previous embodiments, theshot tube outer periphery is cylindrical, other than at the flats.

In another embodiment according to any of the previous embodiments, thealignment structure includes a notch at a forward end of the shot tube.

In another embodiment according to any of the previous embodiments, theinner bore extends through an entire axial length of the shot tube.

In another embodiment according to any of the previous embodiments, theshot tube includes an inner portion formed of a powdered metal and anouter portion formed of stainless steel.

In another embodiment according to any of the previous embodiments, theshot tube outer periphery is cylindrical, other than at the flats.

In another embodiment according to any of the previous embodiments, thealignment structure includes a notch at a forward end of the shot tube.

In another embodiment according to any of the previous embodiments, theinner bore extends through an entire axial length of the shot tube.

In another embodiment according to any of the previous embodiments, theshot tube includes an inner portion formed of a powdered metal and anouter portion formed of stainless steel.

In another embodiment according to any of the previous embodiments, theshot tube includes an inner portion formed of a powdered metal and anouter portion formed of stainless steel.

In another embodiment according to any of the previous embodiments, thealignment structure includes a notch at a forward end of the shot tube.

In another embodiment according to any of the previous embodiments, theinner bore extends through an entire axial length of the shot tube.

In another embodiment according to any of the previous embodiments, theshot tube includes an inner portion formed of a powdered metal and anouter portion formed of stainless steel.

In another embodiment according to any of the previous embodiments, theshot tube includes an inner portion formed of a powdered metal and anouter portion formed of stainless steel.

In another embodiment according to any of the previous embodiments, theinner bore extends through an entire axial length of the shot tube.

In another embodiment according to any of the previous embodiments, theshot tube includes an inner portion formed of a powdered metal and anouter portion formed of stainless steel.

In another embodiment according to any of the previous embodiments, theshot tube includes an inner portion formed of a powdered metal and anouter portion formed of stainless steel.

In another embodiment according to any of the previous embodiments, theshot tube outer periphery is cylindrical, other than at the flats.

These and other features may be best understood from the followingdrawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a die-cast machine.

FIG. 2 shows a detail of a shot tube.

FIG. 3 is a cross-sectional view through a shot tube according to thisapplication.

DETAILED DESCRIPTION

A die-cast machine 10 is illustrated in FIG. 1. As shown, a fixed moldhalf 23 is associated with a moveable mold half 21 to form an overallmold 20. While the two halves are disclosed to form the mold 20,additional mold inserts can be used to form the details of the cavity.

A cavity 22 is formed between the bodies of fixed and moveable halves 23and 21. A fixed platan 28 mounts the fixed mold half 23, and moveableplatan 24 moves with a piston and cylinder combination 26 such that themoveable die half 21 can be moved away from the fixed mold half 23 forremoval of a component after the component has solidified in the cavity22.

A vacuum chamber 34 includes an ingot 38 of a metal to be used forforming the component. An electron beam device 36 melts the ingot 38,which then falls into a copper crucible 40. From the copper crucible 40,molten metal passes through an opening 42 in an outer periphery of ashot tube 30. As shown, the shot tube 30 has a forward end 32 extendinginto the fixed mold half 23.

The molten material is shown at 44 within a bore 99 of the shot tube 30.A piston 48 is driven by a plunger 46 to urge the molten material intothe cavity 22.

The inner bore 99 can be seen to extend through an entire axial lengthof the shot tube 20.

During use, the shot tubes 30 wear and must be replaced. In the priorart, the shot tube has been mounted in the fixed platan 23.

According to this disclosure, however, the shot tube 30 is mounted withits forward end 32 extending through the fixed platan 28 and into anaperture in the fixed mold half 23. As shown, flats 108 are formed at anouter periphery of the shot tube 30, and plungers 104 are selectivelybiased into the flats 108 to secure the shot tube 30 within the fixedmold half 23.

In the illustrated embodiment, a source of hydraulic fluid 100 deliversfluid to passages 102, and into a chamber 106 to urge the plungers 104into the flats 108. The hydraulic fluid can be released from chambers106 to allow removal of the shot tube 30.

While flats 108 are shown, other shaped surfaces may be utilized toreceive a locking member, such as plungers 104.

As also shown, an alignment structure 110 includes a tooth that fitsinto a notch 112 to properly position the shot tube 30 circumferentiallyrelative to the fixed mold half 23.

FIG. 3 shows the shot tube 30 having the flats 108 at opposedcircumferential sides and the notch 112 at a forward end. The structureof the shot tube 30 has an inner powdered metal portion 120 and an outerstainless steel portion 122.

As can be appreciated, an outer periphery of the shot tube 32 iscylindrical, other than at the flats 108.

With this arrangement, the shot tube 30 may be easily replaced. Toreplace the shot tube 30, one merely removes the biased force of thehydraulic fluid, such that the plungers 104 move outwardly of the flats108. The shot tube 30 may then be removed and a new shot tube inserted.

Although an embodiment of this invention has been disclosed, a worker ofordinary skill in this art would recognize that certain modificationswould come within the scope of this invention. For that reason, thefollowing claims should be studied to determine the true scope andcontent of this invention.

1. A shot tube comprising: an inner bore for delivering molten materialinto a die-cast mold, said shot tube having an outer peripheral surfacewith at least one surface for receiving a locking member to lock theshot tube into a fixed mold portion and an alignment structure forproperly aligning the shot tube in the fixed mold portion; and anopening for receiving molten material into the inner bore.
 2. The shottube as set forth in claim 1, wherein said surface includes a pair ofsurfaces formed at an outer periphery of the shot tube.
 3. The shot tubeas set forth in claim 2, wherein said pair of surfaces are flats.
 4. Theshot tube as set forth in claim 3, wherein said shot tube outerperiphery is cylindrical, other than at the flats.
 5. The shot tube asset forth in claim 4, wherein said alignment structure includes a notchat a forward end of said shot tube.
 6. The shot tube as set forth inclaim 5, wherein said inner bore extends through an entire axial lengthof said shot tube.
 7. The shot tube as set forth in claim 6, whereinsaid shot tube includes an inner portion formed of a powdered metal andan outer portion formed of stainless steel.
 8. The shot tube as setforth in claim 1, wherein said shot tube outer periphery is cylindrical,other than at the flats.
 9. The shot tube as set forth in claim 8,wherein said alignment structure includes a notch at a forward end ofsaid shot tube.
 10. The shot tube as set forth in claim 9, wherein saidinner bore extends through an entire axial length of said shot tube. 11.The shot tube as set forth in claim 10, wherein said shot tube includesan inner portion formed of a powdered metal and an outer portion formedof stainless steel.
 12. The shot tube as set forth in claim 2, whereinsaid shot tube includes an inner portion formed of a powdered metal andan outer portion formed of stainless steel.
 13. The shot tube as setforth in claim 1, wherein said alignment structure includes a notch at aforward end of said shot tube.
 14. The shot tube as set forth in claim13, wherein said inner bore extends through an entire axial length ofsaid shot tube.
 15. The shot tube as set forth in claim 14, wherein saidshot tube includes an inner portion formed of a powdered metal and anouter portion formed of stainless steel.
 16. The shot tube as set forthin claim 13, wherein said shot tube includes an inner portion formed ofa powdered metal and an outer portion formed of stainless steel.
 17. Theshot tube as set forth in claim 1, wherein said inner bore extendsthrough an entire axial length of said shot tube.
 18. The shot tube asset forth in claim 17, wherein said shot tube includes an inner portionformed of a powdered metal and an outer portion formed of stainlesssteel.
 19. The shot tube as set forth in claim 1, wherein said shot tubeincludes an inner portion formed of a powdered metal and an outerportion formed of stainless steel.
 20. The shot tube as set forth inclaim 19, wherein said shot tube outer periphery is cylindrical, otherthan at the flats.